Fix file sharing load speed and move error; misc updates

- Remove recursive directory size calculations (single Seafile API call per list)
- Remove 'Used in this location' usage display
- Fix move using v2 per-type endpoints instead of broken batch endpoint
- Send entry type from frontend for correct move routing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

supabase/migrations/20260428103000_prevent_duplicate_requests.sql

@@ -0,0 +1,16 @@
+alter table public.tasks
+  add column if not exists request_key uuid;
+
+alter table public.submissions
+  add column if not exists request_key uuid;
+
+create unique index if not exists tasks_request_key_key
+  on public.tasks (request_key)
+  where request_key is not null;
+
+create unique index if not exists submissions_request_key_key
+  on public.submissions (request_key)
+  where request_key is not null;
+
+create unique index if not exists projects_company_normalized_name_key
+  on public.projects (company_id, lower(btrim(name)));